Ue-rs-based open-loop and semi-open-loop mimo

ABSTRACT

Design of precoding and feedback for user equipment (UE)-specific reference signals (UE-RS)-based open-loop and semi-open-loop multiple input, multiple output (MIMO) systems is discussed. Aspects of the present disclosure provide for sub-resource block (RB) random precoding that allows for greater diversity gain in a lower bandwidth. In addition, the recoding may be performed using resource element (RE)-level layer shifting that provides for a number of precoders to be assigned to a number of layers for every such continuous subcarrier. As such, two codewords may experience the same effective channel quality with channel quality indicators (CQI) being averaged across all of the layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of PCT/CN2016/078312, entitled,“UE-RS-BASED OPEN-LOOP AND SEMI-OPEN-LOOP MIMO,” filed on Apr. 1, 2016,which is expressly incorporated by reference herein in its entirety.

BACKGROUND Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to user equipment (UE)reference signal (UE-RS)-based open-loop and semi-open-loop multipleinput, multiple output (MIMO).

Background

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, and the like. These wireless networks may be multiple-accessnetworks capable of supporting multiple users by sharing the availablenetwork resources. Such networks, which are usually multiple accessnetworks, support communications for multiple users by sharing theavailable network resources. One example of such a network is theUniversal Terrestrial Radio Access Network (UTRAN). The UTRAN is theradio access network (RAN) defined as a part of the Universal MobileTelecommunications System (UMTS), a third generation (3G) mobile phonetechnology supported by the 3rd Generation Partnership Project (3GPP).Examples of multiple-access network formats include Code DivisionMultiple Access (CDMA) networks, Time Division Multiple Access (TDMA)networks, Frequency Division Multiple Access (FDMA) networks, OrthogonalFDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.

A wireless communication network may include a number of base stationsor node Bs that can support communication for a number of userequipments (UEs). A UE may communicate with a base station via downlinkand uplink. The downlink (or forward link) refers to the communicationlink from the base station to the UE, and the uplink (or reverse link)refers to the communication link from the UE to the base station.

A base station may transmit data and control information on the downlinkto a UE and/or may receive data and control information on the uplinkfrom the UE. On the downlink, a transmission from the base station mayencounter interference due to transmissions from neighbor base stationsor from other wireless radio frequency (RF) transmitters. On the uplink,a transmission from the UE may encounter interference from uplinktransmissions of other UEs communicating with the neighbor base stationsor from other wireless RF transmitters. This interference may degradeperformance on both the downlink and uplink.

As the demand for mobile broadband access continues to increase, thepossibilities of interference and congested networks grows with more UEsaccessing the long-range wireless communication networks and moreshort-range wireless systems being deployed in communities. Research anddevelopment continue to advance the UMTS technologies not only to meetthe growing demand for mobile broadband access, but to advance andenhance the user experience with mobile communications.

SUMMARY

In one aspect of the disclosure, a method of wireless communicationincludes randomly selecting a first precoder associated with a firsttransmission block, wherein the first transmission block includes oneof: a first resource block, a first set of bundled resource blocks, or afirst sub-resource block selected as a group of contiguous resourceelements within a resource block, transmitting user equipment(UE)-specific reference signals (UE-RS) and data within the firsttransmission block, wherein the UE-RS and data are precoded using thefirst precoder, selecting a next precoder associated with a nexttransmission block, wherein the next transmission block includes one of:a next resource block, a next set of bundled resource blocks, or a nextsub-resource block selected as a next group of contiguous resourceelements within the resource block, and transmitting the UE-RS and datain the next transmission block, wherein the UE-RS and data are precodedwith a next precoder.

In an additional aspect of the disclosure, a method of wirelesscommunication includes obtaining a first port virtualization matrix formapping a predetermined number of antennas into a subset of virtualizedantenna ports, transmitting in a first transmission block a UE-RSprecoded with the first port virtualization matrix, wherein the firsttransmission block is one of: a first resource block or a first set ofbundled resource blocks, precoding data using a random beamformer,wherein the random beamformer includes the first port virtualizationmatrix and a second precoding matrix selected from a set of precodingmatrices associated with the subset of virtualized antenna ports, andtransmitting the precoded data in the first transmission block.

In an additional aspect of the disclosure, a method of wirelesscommunication includes measuring a reference signal received from a basestation, determining a set of wideband and subband precoders associatedwith a configured antenna array, transmitting a rank indicator, whereinthe rank indicator corresponds to a number of useful layers in atransmission channel, transmitting a precoding matrix indicator (PMI),wherein the PMI is associated with a wideband precoding matrix selectedfrom a set of predetermined wideband precoders, and transmitting achannel quality indicator (CQI) generated based on the measuredreference signal, wherein the channel quality indicator is generatedaccording to an assumption that precoder elements are cycled from a setof predetermined subband precoders.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for randomly selecting a firstprecoder associated with a first transmission block, wherein the firsttransmission block includes one of: a first resource block, a first setof bundled resource blocks, or a first sub-resource block selected as agroup of contiguous resource elements within a resource block, means fortransmitting UE-RS and data within the first transmission block, whereinthe UE-RS and data are precoded using the first precoder, means forselecting a next precoder associated with a next transmission block,wherein the next transmission block includes one of: a next resourceblock, a next set of bundled resource blocks, or a next sub-resourceblock selected as a next group of contiguous resource elements withinthe resource block, and means for transmitting the UE-RS and data in thenext transmission block, wherein the UE-RS and data are precoded with anext precoder.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for obtaining a first portvirtualization matrix for mapping a predetermined number of antennasinto a subset of virtualized antenna ports, means for transmitting in afirst transmission block a UE-RS precoded with the first portvirtualization matrix, wherein the first transmission block is one of: afirst resource block or a first set of bundled resource blocks, meansfor precoding data using a random beamformer, wherein the randombeamformer includes the first port virtualization matrix and a secondprecoding matrix selected from a set of precoding matrices associatedwith the subset of virtualized antenna ports, and means for transmittingthe precoded data in the first transmission block.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for measuring a reference signalreceived from a base station, means for determining a set of widebandand subband precoders associated with a configured antenna array, meansfor transmitting a rank indicator, wherein the rank indicatorcorresponds to a number of useful layers in a transmission channel,means for transmitting a PMI, wherein the PMI is associated with awideband precoding matrix selected from a set of predetermined widebandprecoders, and means for transmitting a CQI generated based on themeasured reference signal, wherein the channel quality indicator isgenerated according to an assumption that precoder elements are cycledfrom a set of predetermined subband precoders.

In an additional aspect of the disclosure, a non-transitorycomputer-readable medium having program code recorded thereon. Theprogram code further includes code to randomly select a first precoderassociated with a first transmission block, wherein the firsttransmission block includes one of: a first resource block, a first setof bundled resource blocks, or a first sub-resource block selected as agroup of contiguous resource elements within a resource block, code totransmit UE-RS and data within the first transmission block, wherein theUE-RS and data are precoded using the first precoder, code to select anext precoder associated with a next transmission block, wherein thenext transmission block includes one of: a next resource block, a nextset of bundled resource blocks, or a next sub-resource block selected asa next group of contiguous resource elements within the resource block,and code to transmit the UE-RS and data in the next transmission block,wherein the UE-RS and data are precoded with a next precoder.

In an additional aspect of the disclosure, a non-transitorycomputer-readable medium having program code recorded thereon. Theprogram code further includes code to obtain a first port virtualizationmatrix for mapping a predetermined number of antennas into a subset ofvirtualized antenna ports, code to transmit in a first transmissionblock a UE-RS precoded with the first port virtualization matrix,wherein the first transmission block is one of: a first resource blockor a first set of bundled resource blocks, code to precode data using arandom beamformer, wherein the random beamformer includes the first portvirtualization matrix and a second precoding matrix selected from a setof precoding matrices associated with the subset of virtualized antennaports, and code to transmit the precoded data in the first transmissionblock.

In an additional aspect of the disclosure, a non-transitorycomputer-readable medium having program code recorded thereon. Theprogram code further includes code to measure a reference signalreceived from a base station, code to determine a set of wideband andsubband precoders associated with a configured antenna array, code totransmit a rank indicator, wherein the rank indicator corresponds to anumber of useful layers in a transmission channel, code to transmit aPMI, wherein the PMI is associated with a wideband precoding matrixselected from a set of predetermined wideband precoders, and code totransmit a CQI generated based on the measured reference signal, whereinthe channel quality indicator is generated according to an assumptionthat precoder elements are cycled from a set of predetermined subbandprecoders.

In an additional aspect of the disclosure, an apparatus configured forwireless communication is disclosed. The apparatus includes at least oneprocessor, and a memory coupled to the processor. The processor isconfigured to randomly select a first precoder associated with a firsttransmission block, wherein the first transmission block includes oneof: a first resource block, a first set of bundled resource blocks, or afirst sub-resource block selected as a group of contiguous resourceelements within a resource block, to transmit UE-RS and data within thefirst transmission block, wherein the UE-RS and data are precoded usingthe first precoder, to select a next precoder associated with a nexttransmission block, wherein the next transmission block includes one of:a next resource block, a next set of bundled resource blocks, or a nextsub-resource block selected as a next group of contiguous resourceelements within the resource block, and to transmit the UE-RS and datain the next transmission block, wherein the UE-RS and data are precodedwith a next precoder.

In an additional aspect of the disclosure, an apparatus configured forwireless communication is disclosed. The apparatus includes at least oneprocessor, and a memory coupled to the processor. The processor isconfigured to obtain a first port virtualization matrix for mapping apredetermined number of antennas into a subset of virtualized antennaports, to transmit in a first transmission block a UE-RS precoded withthe first port virtualization matrix, wherein the first transmissionblock is one of: a first resource block or a first set of bundledresource blocks, to precode data using a random beamformer, wherein therandom beamformer includes the first port virtualization matrix and asecond precoding matrix selected from a set of precoding matricesassociated with the subset of virtualized antenna ports, and to transmitthe precoded data in the first transmission block.

In an additional aspect of the disclosure, an apparatus configured forwireless communication is disclosed. The apparatus includes at least oneprocessor, and a memory coupled to the processor. The processor isconfigured to measure a reference signal received from a base station,to determine a set of wideband and subband precoders associated with aconfigured antenna array, to transmit a rank indicator, wherein the rankindicator corresponds to a number of useful layers in a transmissionchannel, to transmit a PMI, wherein the PMI is associated with awideband precoding matrix selected from a set of predetermined widebandprecoders, and to transmit a CQI generated based on the measuredreference signal, wherein the channel quality indicator is generatedaccording to an assumption that precoder elements are cycled from a setof predetermined subband precoders.

The foregoing has outlined rather broadly the features and technicaladvantages of examples according to the disclosure in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter. The conceptionand specific examples disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present disclosure. Such equivalent constructions do notdepart from the scope of the appended claims. Characteristics of theconcepts disclosed herein, both their organization and method ofoperation, together with associated advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. Each of the figures is provided for the purpose ofillustration and description, and not as a definition of the limits ofthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 is a block diagram illustrating details of a wirelesscommunication system.

FIG. 2 is a block diagram conceptually illustrating a design of a basestation/eNB and a UE configured according to one aspect of the presentdisclosure.

FIG. 3 is a block diagram illustrating a typical 2D active antennaarray.

FIG. 4 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure.

FIGS. 5A and 5B are block diagrams illustrating resource blocks havingsub-RB-based transmission blocks according to aspects of the presentdisclosure.

FIGS. 6A and 6B are block diagrams illustrating transmission streams ofan eNB configured according to aspects of the present disclosure.

FIG. 7 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure.

FIG. 8 is a block diagram illustrating a resource block considered forUE-RS based open-loop or semi-open-loop MIMO with SFBC block coding.

FIG. 9 is a block diagram illustrating an eNB configured according toone aspect of the present disclosure for mapping an SFBC block acrosstwo RBs in the same bundling RB set.

FIG. 10 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure for semi-open-loop MIMO.

FIG. 11A is a block diagram illustrating a UE and eNB configuredaccording to one aspect of the present disclosure.

FIGS. 11B and 11C are block diagrams illustrating CSI reporting betweenUE and eNB configured according to aspects of the present disclosure.

FIG. 12 is a block diagram illustrating an eNB configured according toone aspect of the present disclosure.

FIG. 13 is a block diagram illustrating a UE configured according to oneaspect of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of various possibleconfigurations and is not intended to limit the scope of the disclosure.Rather, the detailed description includes specific details for thepurpose of providing a thorough understanding of the inventive subjectmatter. It will be apparent to those skilled in the art that thesespecific details are not required in every case and that, in someinstances, well-known structures and components are shown in blockdiagram form for clarity of presentation.

This disclosure relates generally to providing or participating inauthorized shared access between two or more wireless communicationssystems, also referred to as wireless communications networks. Invarious embodiments, the techniques and apparatus may be used forwireless communication networks such as code division multiple access(CDMA) networks, time division multiple access (TDMA) networks,frequency division multiple access (FDMA) networks, orthogonal FDMA(OFDMA) networks, single-carrier FDMA (SC-FDMA) networks, LTE networks,GSM networks, as well as other communications networks. As describedherein, the terms “networks” and “systems” may be used interchangeably.

A CDMA network may implement a radio technology such as universalterrestrial radio access (UTRA), cdma2000, and the like. UTRA includeswideband-CDMA (W-CDMA) and low chip rate (LCR). CDMA2000 covers IS-2000,IS-95, and IS-856 standards.

A TDMA network may implement a radio technology such as Global Systemfor Mobile Communications (GSM). 3GPP defines standards for the GSM EDGE(enhanced data rates for GSM evolution) radio access network (RAN), alsodenoted as GERAN. GERAN is the radio component of GSM/EDGE, togetherwith the network that joins the base stations (for example, the Ater andAbis interfaces) and the base station controllers (A interfaces, etc.).The radio access network represents a component of a GSM network,through which phone calls and packet data are routed from and to thepublic switched telephone network (PSTN) and Internet to and fromsubscriber handsets, also known as user terminals or user equipments(UEs). A mobile phone operator's network may comprise one or moreGERANs, which may be coupled with UTRANs in the case of a UMTS/GSMnetwork. An operator network may also include one or more LTE networks,and/or one or more other networks. The various different network typesmay use different radio access technologies (RATs) and radio accessnetworks (RANs).

An OFDMA network may implement a radio technology such as evolved UTRA(E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, flash-OFDM and thelike. UTRA, E-UTRA, and GSM are part of universal mobiletelecommunication system (UMTS). In particular, long term evolution(LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS andLTE are described in documents provided from an organization named “3rdGeneration Partnership Project” (3GPP), and cdma2000 is described indocuments from an organization named “3rd Generation Partnership Project2” (3GPP2). These various radio technologies and standards are known orare being developed. For example, the 3rd Generation Partnership Project(3GPP) is a collaboration between groups of telecommunicationsassociations that aims to define a globally applicable third generation(3G) mobile phone specification. 3GPP long term evolution (LTE) is a3GPP project aimed at improving the universal mobile telecommunicationssystem (UMTS) mobile phone standard. The 3GPP may define specificationsfor the next generation of mobile networks, mobile systems, and mobiledevices. For clarity, certain aspects of the apparatus and techniquesmay be described below for LTE implementations or in an LTE-centric way,and LTE terminology may be used as illustrative examples in portions ofthe description below; however, the description is not intended to belimited to LTE applications. Indeed, the present disclosure is concernedwith shared access to wireless spectrum between networks using differentradio access technologies or radio air interfaces.

A new carrier type based on LTE/LTE-A including in unlicensed spectrumhas also been suggested that can be compatible with carrier-grade WiFi,making LTE/LTE-A with unlicensed spectrum an alternative to WiFi.LTE/LTE-A, when operating in unlicensed spectrum, may leverage LTEconcepts and may introduce some modifications to physical layer (PHY)and media access control (MAC) aspects of the network or network devicesto provide efficient operation in the unlicensed spectrum and meetregulatory requirements. The unlicensed spectrum used may range from aslow as several hundred Megahertz (MHz) to as high as tens of Gigahertz(GHz), for example. In operation, such LTE/LTE-A networks may operatewith any combination of licensed or unlicensed spectrum depending onloading and availability. Accordingly, it may be apparent to one ofskill in the art that the systems, apparatus and methods describedherein may be applied to other communications systems and applications.

System designs may support various time-frequency reference signals forthe downlink and uplink to facilitate beamforming and other functions. Areference signal is a signal generated based on known data and may alsobe referred to as a pilot, preamble, training signal, sounding signal,and the like. A reference signal may be used by a receiver for variouspurposes such as channel estimation, coherent demodulation, channelquality measurement, signal strength measurement, and the like. MIMOsystems using multiple antennas generally provide for coordination ofsending of reference signals between antennas; however, LTE systems donot in general provide for coordination of sending of reference signalsfrom multiple base stations or eNBs.

In some implementations, a system may utilize time division duplexing(TDD). For TDD, the downlink and uplink share the same frequencyspectrum or channel, and downlink and uplink transmissions are sent onthe same frequency spectrum. The downlink channel response may thus becorrelated with the uplink channel response. Reciprocity may allow adownlink channel to be estimated based on transmissions sent via theuplink. These uplink transmissions may be reference signals or uplinkcontrol channels (which may be used as reference symbols afterdemodulation). The uplink transmissions may allow for estimation of aspace-selective channel via multiple antennas.

In LTE implementations, orthogonal frequency division multiplexing(OFDM) is used for the downlink—that is, from a base station, accesspoint or eNodeB (eNB) to a user terminal or UE. Use of OFDM meets theLTE requirement for spectrum flexibility and enables cost-efficientsolutions for very wide carriers with high peak rates, and is awell-established technology. For example, OFDM is used in standards suchas IEEE 802.11a/g, 802.16, High Performance Radio LAN-2 (HIPERLAN-2,wherein LAN stands for Local Area Network) standardized by the EuropeanTelecommunications Standards Institute (ETSI), Digital VideoBroadcasting (DVB) published by the Joint Technical Committee of ETSI,and other standards.

Time frequency physical resource blocks (also denoted here in asresource blocks or “RBs” for brevity) may be defined in OFDM systems asgroups of transport carriers (e.g. sub-carriers) or intervals that areassigned to transport data. The RBs are defined over a time andfrequency period. Resource blocks are comprised of time-frequencyresource elements (also denoted here in as resource elements or “REs”for brevity), which may be defined by indices of time and frequency in aslot. Additional details of LTE RBs and REs are described in the 3GPPspecifications, such as, for example, 3GPP TS 36.211.

UMTS LTE supports scalable carrier bandwidths from 20 MHz down to 1.4MHZ. In LTE, an RB is defined as 12 sub-carriers when the subcarrierbandwidth is 15 kHz, or 24 sub-carriers when the sub-carrier bandwidthis 7.5 kHz. In an exemplary implementation, in the time domain there isa defined radio frame that is 10 ms long and consists of 10 subframes of1 millisecond (ms) each. Every subframe consists of 2 slots, where eachslot is 0.5 ms. The subcarrier spacing in the frequency domain in thiscase is 15 kHz. Twelve of these subcarriers together (per slot)constitute an RB, so in this implementation one resource block is 180kHz. Six Resource blocks fit in a carrier of 1.4 MHz and 100 resourceblocks fit in a carrier of 20 MHz.

Various other aspects and features of the disclosure are furtherdescribed below. It should be apparent that the teachings herein may beembodied in a wide variety of forms and that any specific structure,function, or both being disclosed herein is merely representative andnot limiting. Based on the teachings herein one of an ordinary level ofskill in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. For example,a method may be implemented as part of a system, device, apparatus,and/or as instructions stored on a computer readable medium forexecution on a processor or computer. Furthermore, an aspect maycomprise at least one element of a claim.

FIG. 1 shows a wireless network 100 for communication, which may be anLTE-A network. The wireless network 100 includes a number of evolvednode Bs (eNBs) 105 and other network entities. An eNB may be a stationthat communicates with the UEs and may also be referred to as a basestation, a node B, an access point, and the like. Each eNB 105 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to this particular geographic coveragearea of an eNB and/or an eNB subsystem serving the coverage area,depending on the context in which the term is used.

An eNB may provide communication coverage for a macro cell or a smallcell, such as a pico cell or a femto cell, and/or other types of cell. Amacro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell, suchas a pico cell, would generally cover a relatively smaller geographicarea and may allow unrestricted access by UEs with service subscriptionswith the network provider. A small cell, such as a femto cell, wouldalso generally cover a relatively small geographic area (e.g., a home)and, in addition to unrestricted access, may also provide restrictedaccess by UEs having an association with the femto cell (e.g., UEs in aclosed subscriber group (CSG), UEs for users in the home, and the like).An eNB for a macro cell may be referred to as a macro eNB. An eNB for asmall cell may be referred to as a small cell eNB, a pico eNB, a femtoeNB or a home eNB. In the example shown in FIG. 1, the eNBs 105 a, 105 band 105 c are macro eNBs for the macro cells 110a, 110b and 110c,respectively. The eNBs 105 x, 105 y, and 105 z are small cell eNBs,which may include pico or femto eNBs that provide service to small cells110 x, 110 y, and 110 z, respectively. An eNB may support one ormultiple (e.g., two, three, four, and the like) cells.

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frametiming, and transmissions from different eNBs may be approximatelyaligned in time. For asynchronous operation, the eNBs may have differentframe timing, and transmissions from different eNBs may not be alignedin time.

The UEs 115 are dispersed throughout the wireless network 100, and eachUE may be stationary or mobile. A UE may also be referred to as aterminal, a mobile station, a subscriber unit, a station, or the like. AUE may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, atablet computer, a laptop computer, a cordless phone, a wireless localloop (WLL) station, or the like. A UE may be able to communicate withmacro eNBs, pico eNBs, femto eNBs, relays, and the like. In FIG. 1, alightning bolt (e.g., communication links 125) indicates wirelesstransmissions between a UE and a serving eNB, which is an eNB designatedto serve the UE on the downlink and/or uplink, or desired transmissionbetween eNBs. Wired backhaul communication 134 indicate wired backhaulcommunications that may occur between eNBs.

LTE/-A utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition the system bandwidth into multiple(X) orthogonal subcarriers, which are also commonly referred to astones, bins, or the like. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (X) may bedependent on the system bandwidth. For example, X may be equal to 72,180, 300, 600, 900, and 1200 for a corresponding system bandwidth of1.4, 3, 5, 10, 15, or 20 megahertz (MHz), respectively. The systembandwidth may also be partitioned into sub-bands. For example, asub-band may cover 1.08 MHz, and there may be 1, 2, 4, 8 or 16 sub-bandsfor a corresponding system bandwidth of 1.4, 3, 5, 10, 15, or 20 MHz,respectively.

FIG. 2 shows a block diagram of a design of a base station/eNB 105 and aUE 115, which may be one of the base stations/eNBs and one of the UEs inFIG. 1. For a restricted association scenario, the eNB 105 may be thesmall cell eNB 105 z in FIG. 1, and the UE 115 may be the UE 115 z,which in order to access small cell eNB 105 z, would be included in alist of accessible UEs for small cell eNB 105 z. The eNB 105 may also bea base station of some other type. The eNB 105 may be equipped withantennas 234 a through 234 t, and the UE 115 may be equipped withantennas 252 a through 252 r.

At the eNB 105, a transmit processor 220 may receive data from a datasource 212 and control information from a controller/processor 240. Thecontrol information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. Thedata may be for the PDSCH, etc. The transmit processor 220 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The transmit processor220 may also generate reference symbols, e.g., for the PSS, SSS, andcell-specific reference signal. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 230 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols, if applicable, and may provide output symbol streamsto the modulators (MODs) 232 a through 232 t. Each modulator 232 mayprocess a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 232 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. Downlink signals frommodulators 232 a through 232 t may be transmitted via the antennas 234 athrough 234 t, respectively.

At the UE 115, the antennas 252 a through 252 r may receive the downlinksignals from the eNB 105 and may provide received signals to thedemodulators (DEMODs) 254 a through 254 r, respectively. Eachdemodulator 254 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 254 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 256 may obtainreceived symbols from all the demodulators 254 a through 254 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 258 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 115 to a data sink 260, and provide decoded control informationto a controller/processor 280.

On the uplink, at the UE 115, a transmit processor 264 may receive andprocess data (e.g., for the PUSCH) from a data source 262 and controlinformation (e.g., for the PUCCH) from the controller/processor 280. Thetransmit processor 264 may also generate reference symbols for areference signal. The symbols from the transmit processor 264 may beprecoded by a TX MIMO processor 266 if applicable, further processed bythe modulators 254 a through 254 r (e.g., for SC-FDM, etc.), andtransmitted to the eNB 105. At the eNB 105, the uplink signals from theUE 115 may be received by the antennas 234, processed by thedemodulators 232, detected by a MIMO detector 236 if applicable, andfurther processed by a receive processor 238 to obtain decoded data andcontrol information sent by the UE 115. The processor 238 may providethe decoded data to a data sink 239 and the decoded control informationto the controller/processor 240.

The controllers/processors 240 and 280 may direct the operation at theeNB 105 and the UE 115, respectively. The controller/processor 240and/or other processors and modules at the eNB 105 may perform or directthe execution of various processes for the techniques described herein.The controllers/processor 280 and/or other processors and modules at theUE 115 may also perform or direct the execution of the functional blocksillustrated in FIGS. 4, 7, and 10, and/or other processes for thetechniques described herein. The memories 242 and 282 may store data andprogram codes for the eNB 105 and the UE 115, respectively. A scheduler244 may schedule UEs for data transmission on the downlink and/oruplink.

Multiple-input multiple-output (MIMO) technology generally allowscommunication to take advantage of the spatial dimension through use ofchannel state information (CSI) feedback at the eNB. An eNB maybroadcast cell-specific CSI reference signals (CSI-RS) for which the UEmeasures CSI based on configurations signaled by eNB via RRC, such asCSI-RS resource configuration and transmission mode. The CSI-RS areperiodically transmitted at periodicities of 5, 10, 20, 40, 80 ms, orthe like. A UE may report CSI at CSI reporting instances also configuredby the eNB. As a part of CSI reporting the UE generates and reportschannel quality indicator (CQI), preceding matrix indicator (PMI), andrank indicator (RI). The CSI can be reported either via PUCCH or viaPUSCH and may be reported either periodically or aperiodically, withpotentially different granularity. When reported via PUCCH, the payloadsize for CSI may be limited.

In order to increase system capacity, full-dimensional (FD)-MIMOtechnology has been considered, in which an eNB uses a two-dimensional(2D) active antenna array with a large number of antennas with antennaports having both horizontal and vertical axes, and has a larger numberof transceiver units. For conventional MIMO systems, beamforming hastypically implemented using only azimuth dimension, although of a 3Dmulti-path propagation. However, for FD-MIMO each transceiver unit hasits own independent amplitude and phase control. Such capabilitytogether with the 2D active antenna array allows the transmitted signalto be steered not only in the horizontal direction, as in conventionalmulti-antenna systems, but also simultaneously in both the horizontaland the vertical direction, which provides more flexibility in shapingbeam directions from an eNB to a UE. Providing dynamic beam steering inthe vertical direction has been shown to result in significant gain ininterference avoidance. Thus, FD-MIMO technologies may take advantage ofboth azimuth and elevation beamforming, which would greatly improve MIMOsystem capacity and signal quality.

FIG. 3 is a block diagram illustrating a typical 2D active antenna array30. Active antenna array 30 is a 64-transmitter, cross-polarized uniformplanar antenna array comprising four columns, in which each columnincludes eight cross-polarized vertical antenna elements. Active antennaarrays are often described according to the number of antenna columns(N), the polarization type (P), and the number of vertical elementshaving the same polarization type in one column (M). Thus, activeantenna array 30 has four columns (N=4), with eight vertical (M=8)cross-polarized antenna elements (P=2).

For a 2D array structure, in order to exploit the vertical dimension byelevation beamforming the CSI is needed at the base station. The CSI, interms of PMI, RI, and CQI, can be fed back to the base station by amobile station based on downlink channel estimation and predefined PMIcodebook(s). However, different from the conventional MIMO system, theeNB capable of FD-MIMO is typically equipped with a large scale antennasystem and, thus, the acquisition of full array CSI from the UE is quitechallenging due to the complexity of channel estimation and bothexcessive downlink CSI-RS overhead and uplink CSI feedback overhead.

In LTE, different multi-antenna transmission modes may be employed fordownlink data transmission in order to increase diversity, data rate, orboth. For example, transmit diversity provides for communication usingsignals originating from two or more independent sources modulated withthe same information-bearing signals and that may vary in theirtransmission characteristics at any given instant. In contrast, spatialmultiplexing is a transmission mode in MIMO wireless communications thattransmits independent and separately-encoded data signals or streamsfrom each of the multiple transmit antennas. Spatial multiplexing may beclosed-loop, in which the transmitter has knowledge of the channelconditions through feedback from the receiver, or open-loop, in whichthe transmitter and receiver do not exchange feedback information andthe transmitter figures out the channel conditions on its own. Open-loopspatial multiplexing mode may be more beneficial for medium to highmobility UEs when the reliable PMI feedback is not available at thetransmitter due to fast time update of the spatial channel.

In currently specified systems, open-loop spatial multiplexing issupported for common reference signal (CRS)-based transmission schemes.Two open-loop transmission schemes, e.g. transmit diversity ofspace-frequency block code (SFBC), or spatial multiplexing using a largedelay CDD precoding are supported. For spatial multiplexing with largedelay CDD precoding, both spatial multiplexing gain and diversity gainare achieved. UE-specific reference signal (UE-RS)-based open-loop(without PMI) or semi-open-loop (with reduced PMI) transmission are notyet supported in currently specified systems, but may be provided for inthe future. It is expected that UE-RS based open-loop transmission mayresult in gains over CRS based transmit diversity and spatialmultiplexing. In some configurations, such as 8 CSI-RS ports and 1 CRSport for 2 receive antenna and 4 receive antenna UEs, and 8 CSI-RS portsand 2 CRS ports for 4 receive antenna UEs, open-loop beamforming mayoutperform large delay CDD due to rank limitation. The gain may befurther increased when more antenna ports are configured, such as inFD-MIMO. In addition on multicast-broadcast single frequency network(MBSFN) subframes, using CRS based transmit diversity schemes may belikely to perform poorly due to the absence of CRS in the PDSCH regionand, hence, such a UE-RS based open loop scheme may benefit insupporting efficient data transmission to high speed UEs on MBSFNsubframes.

In the current specification, the precoding for CRS based large delayCDD spatial multiplexing may be defined as follows:

$\begin{matrix}{\begin{bmatrix}{y^{(0)}(i)} \\\vdots \\{y^{({P - 1})}(i)}\end{bmatrix} = {{W(i)}{D(i)}{U\begin{bmatrix}{x^{(0)}(i)} \\\vdots \\{x^{({v - 1})}(i)}\end{bmatrix}}}} & (1)\end{matrix}$

Where y^((p))(i) is the precoded transmitted signal, p is the antennaport index for P antennas, W(i) a random beamformer, D(i) is the CDDmatrix, U is a discrete Fourier transform (DFT) rotational matrix, andx(i) is the data for transmission. The precoding matrix concatenatesthree matrices. The random beamformer, W(i), may be selected from a 2transmit antenna (Tx)/4Tx codebook. The random beamformer, W(i), maychange every v subcarriers and, for every v contiguous subcarriers, vbeams may be formed when the channel rank v is greater than one. Withinthe v contiguous subcarriers, the CDD matrix, D(i), is a v×v diagonalmatrix that assigns a different delay to the v beams, while the DFTrotational matrix, U, is a v×v matrix that maps the v beams to v datasymbols. The matrix, U, may also implement averaging of channel qualityindicator (CQI) measurements across all the layers and, thus, thedifference in the CQI between two codewords may be unnecessary, leavingjust one CQI to be reported by a UE for ranks greater than 1.

Several precoding schemes have been proposed for UE-RS-based open-loopspatial multiplexing. In a first proposed scheme (Scheme 1), both UE-RSand data (PDSCH) are precoded using the same random beamformer, whichmay stay constant for each RB or multiple bundled RBs when precodingbundling is configured. That is:

$\begin{matrix}{\begin{bmatrix}{y^{(0)}(i)} \\\vdots \\{y^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{RB} \right)}\begin{bmatrix}{x^{(0)}(i)} \\\vdots \\{x^{({v - 1})}(i)}\end{bmatrix}}} & (2)\end{matrix}$

It should be noted that a similar precoding structure to closed-loopsingle user (SU)-MIMO may be used for open-loop SU-MIMO, except that aneNB may cyclically assign different precoding elements from the codebookset to different RBs for PDSCH transmission instead of using the PMIfeedback from a UE.

It should further be noted that the random precoding may be extendedalso to a dual codebook with W(i_(RB))=W₁W₂(i_(RB)), where W₁ is along-term wideband precoding matrix of size P×N_(b) and W₂(i_(RB)) is anRB- or RB bundling-based random precoding matrix of size N_(b)×v andcyclically selected among the precoder elements in the W₂ codebook. W₁can be fed back by a UE for semi-open-loop MIMO operation or may berandomly selected from the predetermined codebook set when open-loopMIMO is configured without PMI feedback.

In a second proposed scheme for UE-RS-based open-loop spatialmultiplexing (Scheme 2), a modified large delay CDD precoding may beimplemented by using a different beamformer for UE-RS and datatransmissions. That is, for UE-RS, a per RB or per RB bundling-basedrandom beamforming W(i_(RB)) may be applied. For the data symbols inPDSCH, the W(i_(RB)), D(i), and U matrices may be used for precoding.The CDD matrix D(i) may change from data resource element (RE)subcarrier to subcarrier, similar to the operational characteristics oftransmission mode 3 (TM3). Scheme 2 may be described according to thefollowing:

$\begin{bmatrix}{y_{p}^{(0)}(i)} \\\vdots \\{y_{p}^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{RB} \right)}\begin{bmatrix}{x_{p}^{(0)}(i)} \\\vdots \\{x_{p}^{({v - 1})}(i)}\end{bmatrix}}$

for UE-RS, and

$\begin{bmatrix}{y_{d}^{(0)}(i)} \\\vdots \\{y_{d}^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{RB} \right)}D(i){U\begin{bmatrix}{x_{d}^{(0)}(i)} \\\vdots \\{x_{d}^{({v - 1})}(i)}\end{bmatrix}}}$

for data. Similar to Scheme 1, Scheme 2 may also be extended to a dualcodebook with W(i_(RB))=W₁W₂(i_(RB)), where W₁ is long-term widebandprecoding matrix of size P×N_(b) and W₂(i_(RB)) is an RB- or RBbundling-based random precoding matrix of size N_(b)×V and cyclicallyselected among the precoder elements in the W₂ codebook. W₁ may be fedback by the UE for semi-open-loop MIMO operation or randomly selectedfrom the predetermined wideband codebook set when open-loop MIMO isconfigured without PMI feedback.

For Scheme 1, a larger bandwidth may be used in order to achievesufficient frequency selectivity by random precoding W(i_(RB)) while asmall/medium bandwidth allocation may achieve limited diversity gain.Compared to Scheme 1, increased frequency selectivity can be observed inScheme 2 due to the diversity effect of the CDD matrix, D(i). However,for RBs in the same bundling set, the frequency selectivity would beachieved by cycling over the V precoder elements using the CDD matrix,D(i). A question may arise whether there is performance degradation whencombining the large delay CDD precoding with dual codebook structurebased W(i_(RB)). For example, dual codebook based W(i_(RB)) can be givenby:

${{W\left( i_{RB} \right)} = {{{\frac{1}{\sqrt{2}}\begin{bmatrix}u_{1} & u_{2} \\{e^{j\; \varphi}u_{1}} & {{- e^{j\; \varphi}}u_{2}}\end{bmatrix}}\mspace{14mu} {for}\mspace{14mu} v} = 2}},{and}$${W\left( i_{RB} \right)} = {\frac{1}{\sqrt{2}}\begin{bmatrix}u_{1} & u_{1} & u_{2} & u_{2} \\{e^{j\; \varphi}u_{1}} & {{- e^{j\; \varphi}}u_{1}} & {e^{j\; \varphi}u_{2}} & {{- e^{j\; \varphi}}u_{2}}\end{bmatrix}}$

for v=4, where e^(jϕ)=1 or j, u₁ and u₂ are DFT precoding vectorsselected from the W₁ codebook set.

If the D(i) and the U matrices are defined similarly to the 2/4 CRSports in TM3, the combined precoder for data symbols may be representedas:

${W = {{\begin{bmatrix}\frac{u_{1} + u_{2}}{2} & \frac{u_{1} - u_{2}}{2} \\{e^{j\; \varphi}\frac{u_{1} - u_{2}}{2}} & {e^{j\; \varphi}\frac{u_{1} + u_{2}}{2}}\end{bmatrix}\mspace{14mu} {for}\mspace{14mu} v} = 2}},{and}$$W = \begin{bmatrix}\frac{u_{1} + u_{2}}{\sqrt{2}} & \frac{u_{1} - u_{2}}{2} & 0 & \frac{u_{1} - u_{2}}{2} \\0 & {j\; e^{j\; \varphi}\frac{u_{1} - u_{2}}{2}} & \frac{u_{1} + u_{2}}{\sqrt{2}} & {{- {je}^{j\; \varphi}}\frac{u_{1} - u_{2}}{2}}\end{bmatrix}$

for v=4. For each V continuous subcarriers, the eNB cyclically assignsthe V data symbols to the v beams formed by the combined precodingmatrix W. The benefit of the CDD precoding may be reduced, however, bycorrelation of the two DFT vectors u₁ and u₂, and the data transmissionfrom one polarization instead of two polarizations may not fully utilizethe spatial diversity of the channel.

FIG. 4 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure. The example blocks ofFIG. 4 define an improvement to Scheme 1 of the UE-RS based open-loopand semi-open-loop spatial multiplexing. The example blocks will also bedescribed with respect to eNB 60 as illustrated in FIG. 12. FIG. 12 is ablock diagram illustrating eNB 60 configured according to one aspect ofthe present disclosure. eNB 60 includes the structure, hardware, andcomponents as illustrated for UE 105 of FIG. 2. For example, eNB 60includes controller/processor 240, which operates to execute logic orcomputer instructions stored in memory 242, as well as controlling thecomponents of eNB 60 that provide the features and functionality of eNB60. eNB 60, under control of controller/processor 240, transmits andreceives signals via wireless radios 1201 a-t and antennas 234 a-t.Wireless radios 1201 a-t includes various components and hardware, asillustrated in FIG. 2 for eNB 105, including modulator/demodulators 232a-t, MIMO detector 236, receive processor 238, transmit processor 220,and TX MIMO processor 230.

At block 400, an eNB selects a first precoder associated with a firsttransmission block. For example, eNB 60, under control ofcontroller/processor 240, executes UE-RS MIMO scheme 1202 stored inmemory 242. The execution environment of executing UE-RS MIMO scheme1202 determines whether the improved aspects of Scheme 1 or Scheme 2 areimplemented by eNB 60. In further execution by controller/processor 240of transmission block 1204, eNB 60 may define a transmission block as aRB or a set of bundled RBs, or, in additional aspects of the presentdisclosure, a transmission block may also be a sub-RB. A sub-RB is aselection of contiguous REs within a RB. Each RB may include multiplesub-RB groups selected with different contiguous REs across subcarriers,OFDM symbols, or a combination of both. The sub-RB based transmissionblock operation may be used for a small size resource allocation (e.g.,one or a limited # of RBs). The threshold for selecting such a sub-RBscheme may be hard-coded, RRC configured, or even indicated in DCI. Theselecting performed by the eNB in accordance with the example aspect maybe random, weighted, or the like.

In a first example aspect illustrated in FIG. 4 and defined with asub-RB-based transmission block, at block 401 a, the eNB transmits UE-RSand data within the first transmission block, wherein the UE-RS and dataare precoded using a first precoder. The UE-RS and data are precodedthrough execution of precoder 1203, stored in memory 242, into theselected group of contiguous REs of the RB. Depending on the particularaspect of Scheme improvement under operation, eNB 60 knows whether toprecode both UE-RS and data using the same precoders, or to usedifferent precoding for UE-RS and data.

At block 402, the eNB selects a next precoder associated with a nexttransmission block. For example, the execution environment of UE-RS MIMOscheme 1202 and precoder 1203 direct eNB 60 to select the appropriatebeamformer. Moreover, by the execution environment of transmission block1204 under control of controller/processor 240, defining thetransmission blocks on a sub RB basis, the precoder, W(i_(sub) _(_)_(RB)), may change in each sub-RB group. Multiple different precodersmay be used in transmission of UE-RS and data within the same RB, thus,improving diversity even in small or medium bandwidth allocations ofScheme 1.

In the first example aspect defined with the sub-RB-based transmissionblocks, at block 403 a, the eNB transmits UE-RS and data in the nexttransmission block, wherein the UE-RS and data are precoded using thenext precoder. The UE-RS and data are transmitted via wireless radios1201 a-t and antennas 234 a-t. The random precoding of blocks 401 a and403 a through execution of precoder 1203 may be extended also to a dualcodebook, with W(i_(sub) _(_) _(RB))=W₁W₂(i_(sub) _(_) _(RB)), where W₁is a long-term wideband precoding matrix and W₂(i_(sub) _(_) _(RB)) is asub-RB-based random precoding matrix that is cyclically selected fromthe predetermined set of precoder elements in the W₂ codebook. W₁ can befed back by a UE when configured for semi-open-loop MIMO operation ormay be randomly selected from the predetermined codebook set whenopen-loop MIMO is configured without PMI feedback.

FIGS. 5A and 5B are block diagrams illustrating resource blocks 500 and501 having sub-RB-based transmission blocks according to aspects of thepresent disclosure. The performance of Scheme 1 with small/medium BWallocation can be improved by using a sub-RB level precoding bundlingaccording to the various aspects of the present disclosure. As shownresource block 500 in the FIG. 5A, the 12 UE-RS tones per RB are dividedinto three frequency division multiplex (FDM) groups, each associatedwith one sub-RB transmission block, Sub-RB#0, Sub-RB#1, and Sub-RB#2.The random precoding is applied within each sub-RB transmission blockand the precoder may change across the sub-RBs. That is:

$\begin{matrix}{\begin{bmatrix}{y^{(0)}(i)} \\\vdots \\{y^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{{sub}\_ {RB}} \right)}\begin{bmatrix}{x^{(0)}(i)} \\\vdots \\{x^{({v - 1})}(i)}\end{bmatrix}}} & (3)\end{matrix}$

The partition of one RB into multiple sub-RBs may include other options,such as illustrated by resource block 501 in FIG. 5B, in which case thesub-RB transmission blocks have staggered grouping. For example,resource block 501 is divided into six sub-RB-based transmission blocks,Sub-RB#0-Sub-RB#5.

It should be noted that various additional aspects of the presentdisclosure provide that downlink resource allocation may also be changedfrom a per-RB to a per-sub-RB basis.

Referring back to FIG. 4, in an additional example aspect of the presentdisclosure, after randomly selecting the first precoder, through theexecution environment of precoder 1203, and associated with the firsttransmission block at block 400, the eNB may transmit UE-RS and datawithin the first transmission block via wireless radios 1201 a-t andantennas 234 a-t, wherein the UE-RS is precoded by executing precoder1203 using the first precoder and the data is precoded by executingprecoder 1203 using the first precoder and an RE-level layer permutationmatrix stored at layer shifting matrix 1205, at alternative block 401 b.Instead of precoding the data with only the first precoder, asillustrated in block 401 a, alternative block 401 b allows additionalprecoding of the data with the layer permutation matrix at layershifting matrix 1205, which, when executed under control ofcontroller/processor 240 that causes the data to be shifted by layerswithin the transmission channel via wireless radios 1201 a-t andantennas 234 a-t.

To achieve the RE-level precoder cycling described in alternative block401 b, Scheme 1 may be modified as follows:

$\begin{bmatrix}{y_{p}^{(0)}(i)} \\\vdots \\{y_{p}^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{RB} \right)}\begin{bmatrix}{x_{p}^{(0)}(i)} \\\vdots \\{x_{p}^{({v - 1})}(i)}\end{bmatrix}}$

for UE-RS transmission, and

$\begin{bmatrix}{y_{d}^{(0)}(i)} \\\vdots \\{y_{d}^{({P - 1})}(i)}\end{bmatrix} = {{W\left( i_{RB} \right)}{{U(i)}\begin{bmatrix}{x_{d}^{(0)}(i)} \\\vdots \\{x_{d}^{({v - 1})}(i)}\end{bmatrix}}}$

for data transmission. Where the matrix U(i) is an RE-level layerpermutation matrix stored at layer shifting matrix 1205 in memory 242that cyclically assigns the V beams formed by the matrix W(i_(RB)) todifferent layers within V continuous subcarriers. Examples of the layerpermutation matrix U(i) for v=4 include the following:

-   U(0)=[e₁ e₂ e₃ e₄],-   U(1)=[e₄ e₁ e₂ e₃],-   U(2)=[e₃ e₄ e₁ e₂] and-   U(3)=[e₂ e₃ e₄ e₁]-   where e_(i) is a basis vector with ‘1’ on i^(th) element and ‘0’ on    all other elements. The random precoder W(i_(RB)) may change across    RBs, across sets of bundled RBs, or across sub-RB transmission    blocks based on the configuration and W(i_(RB))=W₁W₂(i_(RB)) for    dual codebook structure.

After selecting the next precoder associated with the next transmissionblock at block 402, the eNB, in the additional example illustrated inFIG. 4, would transmit the UE-RS and data, at block 403 b, within thenext transmission block, wherein the UE-RS is precoded with the nextprecoder, while the data is again precoded not only with the nextprecoder but also using the RE-level layer permutation matrix, U(i).

FIGS. 6A and 6B are block diagrams illustrating transmission streams 600and 601 of eNB 60 configured according to aspects of the presentdisclosure. In FIG. 6A, eNB 60 transmits data without RE-level layershifting, while, in FIG. 6B, eNB 60 uses random precoding with RE-levellayer shift for data transmission. P7, P8, P9 and P10 are precoders forUE-RS port 7, 8, 9 and 10, while X0, X1, X2 and X3 are data symbols ofthe layers 0, 1, 2 and 3. Without RE-level layer shift, as illustratedin transmission stream 600, eNB 60 uses the same precoder for the datasymbols in four continuous subcarriers in which the diversity isobtained through the beamformer changing across RBs. With RE-level layershift, as illustrated in transmission stream 601, eNB 60 cyclicallyassigns the four precoders to four layers for every four continuoussubcarriers and RE-level frequency selectivity is achieved. With thelayer shift, two codewords experience the same effective channel SINRfor rank >1 and CQI averaging may be achieved across all layers.

FIG. 7 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure. At block 700, an eNBobtains a first port virtualization matrix for mapping a predeterminednumber of antennas into a subset of virtualized antenna ports. At block701, the eNB transmits in a first transmission block a UE-RS precoded byexecuting precoder 1203 with the port virtualization matrix 1206 storedin memory 242. According to additional aspects of the presentdisclosure, a modified Scheme 2 uses the RE-level random precoding fromprecoder 1203 for increased frequency selectivity according to thefollowing:

$\begin{bmatrix}{y_{p}^{(0)}(i)} \\\vdots \\{y_{p}^{({P - 1})}(i)}\end{bmatrix} = {{W_{i}\left( i_{RB} \right)}\begin{bmatrix}{x_{p}^{(0)}(i)} \\\vdots \\{x_{p}^{({v - 1})}(i)}\end{bmatrix}}$

for UE-RS precoding and transmission. Where W₁(i_(RB)) is a portvirtualization matrix 1206 with an orthogonal column vector which maps Pantennas into 2 or 4 virtualized ports. W₁(i_(RB)) may be used toprecode UE-RS and may change on per RB or per RB bundling or aper-sub-RB basis. W₁(i_(RB)), can be constructed from a set oforthogonal DFT basis vector, e.g.,

$W_{1} = \begin{bmatrix}u_{1} & 0 \\0 & u_{1}\end{bmatrix}$

for 2-ports and for

$W_{1} = \begin{bmatrix}u_{1} & u_{1} & 0 & 0 \\0 & 0 & u_{2} & u_{2}\end{bmatrix}$

4-ports, where u₁ and u₂ are the DFT vectors from the W₁ codebook set.

At block 702, the eNB precode data by executing precoder 1203, undercontrol of controller/processor 240, using a random beamformer, wherethe random beamformer includes the first port virtualization matrix anda second precoding matrix selected from a set of precoding matricesassociated with the subset of virtualized antenna ports, from UE-RS MIMOscheme 1202 and precoder 1203, and, at block 703, the eNB transmits theprecoded data in the first transmission block via wireless radios 1201a-t and antennas 234 a-t. The modified Scheme 2 uses RE-level randomprecoding for increased frequency selectivity further according to thefollowing:

$\begin{bmatrix}{y_{d}^{(0)}(i)} \\\vdots \\{y_{d}^{({P - 1})}(i)}\end{bmatrix} = {{W(i)}{D(i)}{U\begin{bmatrix}{x_{d}^{(0)}(i)} \\\vdots \\{x_{d}^{({v - 1})}(i)}\end{bmatrix}}}$

for data precoding and transmission. For data symbols, the randombeamformer W(i)=W₁(i_(RB))W₂(i), where W₂(i) is selected from the2Tx/4Tx codebook of size 2×V or 4×v.

Additional aspects of the present disclosure provide that rank 1transmissions with transmit diversity of two layers may be extended toUE-RS-based operations using space frequency block coding (SFBC). Fortransmission on two UE-RS ports, p ∈ {7,8}, the precoding for PDSCH isdefined by:

$\begin{bmatrix}{y^{(0)}\left( {2i} \right)} \\{y^{(1)}\left( {2i} \right)} \\{y^{(0)}\left( {{2i} + 1} \right)} \\{y^{(1)}\left( {{2i} + 1} \right)}\end{bmatrix} = {\begin{bmatrix}{W(i)} & 0 \\0 & {W(i)}\end{bmatrix} \cdot T \cdot \begin{bmatrix}{{Re}\left( {x^{(0)}(i)} \right)} \\{{Re}\left( {x^{(1)}(i)} \right)} \\{{Im}\left( {x^{(0)}(i)} \right)} \\{{Im}\left( {x^{(1)}(i)} \right)}\end{bmatrix}}$ $T = \begin{bmatrix}1 & 0 & j & 0 \\0 & {- 1} & 0 & j \\0 & 1 & 0 & j \\1 & 0 & {- j} & 0\end{bmatrix}$

Where the matrix T is precoding matrix for 2-ports T×D, as defined forCRS based transmit diversity. W(i) is an antenna port virtualizationmatrix of size P×2, which can be the same beamformer used for rank 2open-loop spatial multiplexing: W(i)=W(i_(RB))=W₁W₂(i_(RB)), forsub-RB-based, RB-based, or RB bundling-based random precoding (Scheme1), or W(i)=W₁(i_(RB))W₂(i) for RE-level based random precoding (Scheme2). For UE-RS, a per sub-RB based or RB bundling based random precodingW(i_(RB))=W₁W₂(i_(RB)) (Scheme 1), or W₁(i_(RB)) (Scheme 2) may beapplied.

FIG. 8 is a block diagram illustrating a resource block 80 consideredfor UE-RS based open-loop or semi-open-loop MIMO with SFBC block coding.In currently specified system, an SFBC block, e.g. two REs may not spanacross different OFDM symbols, or across more than three subcarriers inthe frequency domain, or across two RBs. If there is an odd number ofavailable PDSCH REs in a PRB, as in resource block 80, the symbol of theentire RB is skipped. Following same principle for UE-RS based transmitdiversity, for rank 1-2 transmissions on two UE-RS ports, the symbols 5,6, 12 and 13 are unusable for PDSCH transmission which may greatlyreduce the peak throughput.

FIG. 9 is a block diagram illustrating eNB 60 configured according toone aspect of the present disclosure for mapping an SFBC block acrosstwo RBs 900 and 901 in the same bundling RB set 90. Because RB bundlingmay be applied for UE-RS, the above SFBC block mapping restrictions canbe relaxed so that an SFBC block can be mapped across two RBs 900 and901 in the same bundling set 90 if there is an even number of resourceelements for the OFDM symbol containing UE-RS in two continuous resourceblocks assigned for transmission. For example, in OFDM symbols 902 and903, there are an even number of resource elements in the two continuousresource blocks 900 and 901 assigned for transmission.

It should be noted that the sub-RB bundling operation for improvementsto Scheme 1 is used for a small size resource allocation (e.g., one or alimited number of RBs). The threshold for choosing such a sub-RB schememay be hard-coded in a UE, RRC configured, or even indicated in downlinkcontrol information (DCI).

FIG. 10 is a block diagram illustrating example blocks executed toimplement one aspect of the present disclosure for semi-open-loop MIMO.The example blocks of FIG. 10 will also be described with respect to UE1100 as illustrated in FIG. 13. FIG. 13 is a block diagram illustratingUE 1100 configured according to one aspect of the present disclosure. UE1100 includes the structure, hardware, and components as illustrated forUE 115 of FIG. 2. For example, UE 1100 includes controller/processor280, which operates to execute logic or computer instructions stored inmemory 282, as well as controlling the components of UE 1100 thatprovide the features and functionality of UE 1100. UE 1100, undercontrol of controller/processor 280, transmits and receives signals viawireless radios 1301 a-r and antennas 252 a-r. Wireless radios 1301 a-rincludes various components and hardware as illustrated in FIG. 2 for UE115, including demodulator/modulators 254 a-r, MIMO detector 256,receive processor 258, transmit processor 264, and TX MIMO processor266.

At block 1000, a UE measures a reference signal received from a basestation. For example, UE 1100 executes measurement logic 1302, stored inmemory 282, under control of controller/processor 280. At block 1001,the UE determines a set of wideband and subband precoders associatedwith a configured antenna array. For example, UE 1100, under control ofcontroller/processor 280, determines the set of wideband and subbandprecoders within the execution environment of measurement logic 1302 andby accessing precoders 1305, stored in memory 282, for the configuredantenna array of antennas 252 a-r.

At block 1002, the UE transmits a PMI via wireless radios 1301 a-r, andantennas 252 a-r, wherein the PMI is associated with a widebandprecoding matrix selected from a set of predetermined wideband precodersassociated with a configured antenna array. The reported PMI, which maybe constrained by the reported RI, indicates the first PMI of the dualcodebook.

At block 1003, the UE transmits a CQI generated based on the measuredreference signal, wherein the CQI is generated according to anassumption that precoder elements are cycled from a set of predeterminedsubband precoders. The predetermined subband precoders includes the W₂codebook associated with the first PMI. The CQI can be either widebandor subband based on the configuration.

For a rank >1, one CQI is reported for two codewords since the twocodewords may experience the same effective channel quality due to theusage of RE-level layer shifting for data transmission.

It should be noted that when the first precoding matrix of theassociated codebook is an identity matrix, the UE may skip reporting thePMI. Additionally, when the PMI is not reported, the CQI may begenerated according to an assumption that precoder elements are cycledfrom a set of predetermined wideband precoders.

FIG. 11A is a block diagram illustrating a UE 1100 and eNB 60 configuredaccording to one aspect of the present disclosure. In the exampleillustrated in FIG. 11A, UE 1100 is configured to transmit CSI reporting1101 for PUCCH Mode 1-1. UE 1100 send eNB 60 the first CSI report viawireless radios 1301 a-r and antennas 252 a-r, including RI, the secondreport including the first PMI, and the third report including awideband CQI. It should be noted that the period of the third widebandCQI report may be N_(pd) subframes, while the period of the first andsecond reports may be M_(RI)N_(pd) and H′ N_(pd) subframes. M_(RI),N_(pd) and H′ may be configured by the higher-layer signaling from eNB60 and stored at periodicities 1304 in memory 282. The second and thirdreports are configured with the same reporting subframe offset which canbe different from that of the first report. UE 1100, under control ofcontroller/processor 280, will access the periodicities and offsetsstored in periodicities 1304 when executing the CSI report generator1303 to generate and send out the CSI reports.

FIGS. 11B and 11C are block diagrams illustrating CSI reporting 1102 and1103 between UE 1100 and eNB 60 configured according to aspects of thepresent disclosure. For PUCCH Mode 2-1, UE 1100 sends eNB 60 the firstreport including RI and precoding type indicator (PTI), the secondreport including the first PMI for PTI=0, CSI reporting 1102, andwideband CQI for PTI=1, CSI reporting 1103, and the third reportincluding wideband CQI for PTI=0, CSI reporting 1102, and subband CQIfor PTI=1, CSI reporting 1103. It should be noted that the period of thethird report may be N_(pd) subframes. The period of the second reportmay be H′·N_(pd) subframes for first PMI (PTI=0), CSI reporting 1102, orH·N_(pd) subframes for wideband CQI (PTI=1), CSI reporting 1103. Theperiod of the first report may be M_(RI)·H·N_(pd) subframes.

The open loop transmission schemes and associated UE-RS ports and layersare indicated by layer 1 (L1) signaling, as shown in Table 1 below,assuming total single user/multiple user layers no larger than four.When only one codeword is enabled, the first four code points with thevalue 0-3 are used to indicate the rank 1 transmission with singleantenna port mapping. It can be used for both single user/multiple usertransmission. For multiple user transmission, different UEs can bedistinguished by different UE-RS ports or by a scrambling identity of 0and 1. For the next two code points with a value of 4 and 5 for onecodeword case, it may be associated with a rank 1 transmission havingtransmit diversity with UE-RS ports 7-8 assigned. For the value of 6 ofone codeword case, it may be used for retransmission when the associatedtransport block is mapped to 2 layers in the initial transmission. Whenboth of the two codewords are enabled, the first code points with avalue of 0 and 1 are used for rank 2 spatial multiplexing transmissionwith UE-RS ports 7-8. For rank 3 transmission, there may be twoconfigurations, one for UE-RS ports 7-9 and the other for UE-RS ports7-10. The first may be associated with Scheme 1 and the second may beassociated with Scheme 2, where four virtualized ports may be used. Forrank 4 transmission, UE-RS ports 7-10 may be used. It should be notedthat the definition of UE-RS ports 7, 8, 9 and 10 may be same as thatused for close-loop beamforming, e.g., based on an orthogonal cover codeof length 2.

TABLE 1 One codeword: Two codewords: codeword 0 enabled, codeword 0enabled, codeword 1 disabled codeword 1 enabled Value Message ValueMessage 0 1 layer, port 7, n_(SCID) = 0 0 2 layers, ports 7-8 n_(SCID) =0 1 1 layer, port 7, n_(SCID) = 1 1 2 layers, ports 7-8, n_(SCID) = 1 21 layer, port 8, n_(SCID) = 0 2 3 layers, ports 7-9 3 1 layer, port 8,n_(SCID) = 1 3 3 layers, ports 7-9 4 2 layers, TxD, ports 7-8 4 4layers, ports 7-10 n_(SCID) = 0 5 2 layers, TxD, ports 7-8 5 Reservedn_(SCID) = 1 6 2 layers, SM, ports 7-8 6 Reserved 7 Reserved 7 Reserved

Those of skill in the art would understand that various aspects of thepresent disclosure may include different implementations, such asthrough non-transitory computer-readable media, which, when code storedthereon is executed by one or more computers or processors performs thefeatures and functionality of the aspects, and such as throughapparatuses that have one or more processors and memory coupled to theprocessors, such that when instructions are executed, the apparatus maybe configured to perform the features and functionality of the aspects.The following aspects represent statements that reflect the variousaspects of the present disclosure in different formats from the claimsfiled herewith.

The present disclosure comprises a first aspect, such as anon-transitory computer-readable medium having program code recordedthereon, the program code including:

program code for causing a computer to select a first precoderassociated with a first transmission block, wherein the firsttransmission block includes one of: a first resource block, a first setof bundled resource blocks, or a first sub-resource block selected as agroup of contiguous resource elements within a resource block;

program code for causing the computer to transmit user equipment(UE)-specific reference signals (UE-RS) and data within the firsttransmission block, wherein the UE-RS and data are precoded using thefirst precoder;

program code for causing the computer to select a next precoderassociated with a next transmission block, wherein the next transmissionblock includes one of: a next resource block, a next set of bundledresource blocks, or a next sub-resource block selected as a next groupof contiguous resource elements within the resource block; and

program code for causing the computer to transmit the UE-RS and data inthe next transmission block, wherein the UE-RS and data are precodedwith a next precoder.

Based on the first aspect, the non-transitory computer-readable mediumof a second aspect, wherein the first precoder and the next precoder arebased on a product of a wideband precoding matrix and a subbandprecoding matrix, wherein the subband precoding matrix is cyclicallyselected from a set of predetermined precoding matrices.

Based on the second aspect, the non-transitory computer-readable mediumof a third aspect, wherein the wideband precoding matrix is one of:

received from a UE; or

randomly selected from a set of predetermined wideband precodingmatrices.

Based on the first aspect, the non-transitory computer-readable mediumof a fourth aspect, wherein the program code for causing the computer totransmit the UE-RS and data are executed at rank >1, wherein the data isfurther precoded with a layer permutation matrix along with the firstprecoder and the next precoder; wherein the layer permutation matrixcyclically assigns each resulting transmission beam to a different layerwithin a predetermined number of continuous subcarriers.

Based on the first aspect, the non-transitory computer-readable mediumof a fifth aspect, wherein the program code for causing the computer totransmit the UE-RS and data are executed at rank 1 and configured withtransmit diversity, wherein the data is further precoded with a spacefrequency block coding matrix.

Based on the fifth aspect, the non-transitory computer-readable mediumof a sixth aspect, further includes:

program code for causing the computer to determine the firsttransmission block is the first set of bundled resource blocks;

program code for causing the computer to determine presence of an evennumber of resource elements for the data in two continuous resourceblocks of the first set of bundled resource blocks; and

program code for causing the computer to map the data precoded with thespace frequency block coding matrix across two continuous resourceblocks of the first set of bundled resource blocks.

Based on the first aspect, the non-transitory computer-readable mediumof a seventh aspect, further includes:

program code for causing the computer to transmit an indication oftransmission scheme, wherein the indication of transmission scheme isassociated with at least one or more UE-RS ports, the number of usefullayers, a mode of transmit diversity or spatial multiplexing for datatransmission.

Based on the first aspect, the non-transitory computer-readable mediumof an eighth aspect, further includes:

program code for causing the computer to determine the firsttransmission block and the next transmission block based on at least atotal number of scheduled resource blocks, wherein a sub-resource blockis selected only for a small size resource allocation.

The present disclosure comprises a ninth aspect which further comprisesthe non-transitory computer-readable medium of any combination the firstthrough eighth aspects.

The present disclosure comprises a tenth aspect, such as anon-transitory computer-readable medium having program code recordedthereon, the program includes:

program code for causing a computer to obtain a first portvirtualization matrix for mapping a predetermined number of antennasinto a subset of virtualized antenna ports;

program code for causing the computer to transmit in a firsttransmission block a user equipment (UE)-specific reference signal(UE-RS) precoded with the first port virtualization matrix, wherein thefirst transmission block is one of: a first resource block or a firstset of bundled resource blocks;

program code for causing the computer to precode data using a randombeamformer, wherein the random beamformer includes the first portvirtualization matrix and a second precoding matrix selected from a setof precoding matrices associated with the subset of virtualized antennaports; and

program code for causing the computer to transmit the precoded data inthe first transmission block.

Based on the tenth aspect, the non-transitory computer-readable mediumof an eleventh aspect, wherein the program code for causing the computerto obtain the port virtualization matrix includes one of:

program code for causing the computer to receive the port virtualizationmatrix from a UE; or

program code for causing the computer to randomly select a set oforthogonal DFT basis vectors from a predetermined wideband codebook forthe port virtualization matrix.

Based on the tenth aspect, the non-transitory computer-readable mediumof an twelfth aspect, wherein the program code for causing the computerto transmit the UE-RS and data are executed at rank >1, wherein the datais further precoded with a cyclic delay diversity matrix and a discreteFourier transform (DFT) rotational matrix along with the randombeamformer; wherein the cyclic delay diversity matrix and the DFTrotation matrix cyclically assign each resulting transmission beam to adifferent layer within a predetermined number of continuous subcarriers.

Based on the tenth aspect, the non-transitory computer-readable mediumof a thirteenth aspect, wherein the program code for causing thecomputer to transmit the UE-RS and data are executed at rank 1 andconfigured with transmit diversity, wherein the data is further precodedwith a space frequency block coding matrix.

Based on the thirteenth aspect, the non-transitory computer-readablemedium of a fourteenth aspect, further includes:

program code for causing the computer to determine the firsttransmission block is the first set of bundled resource blocks;

program code for causing the computer to determine presence of an evennumber of resource elements for the data in two continuous resourceblocks of the first set of bundled resource blocks; and

program code for causing the computer to map the data precoded with thespace frequency block coding matrix across two resource blocks of thefirst set of bundled resource blocks.

Based on the tenth aspect, the non-transitory computer-readable mediumof a fifteenth aspect, further includes:

program code for causing the computer to transmit an indication oftransmission scheme, wherein the indication of transmission scheme isassociated with at least one or more UE-RS ports, the number of usefullayers, a mode of transmit diversity or spatial multiplexing for datatransmission.

The present disclosure comprises a sixteenth aspect which furthercomprises the non-transitory computer-readable medium of any combinationthe tenth through fifteenth aspects.

The present disclosure comprises a seventeenth aspect, such as anon-transitory computer-readable medium having program code recordedthereon, the program code comprising:

program code for causing a computer to measure a reference signalreceived from a base station;

program code for causing the computer to determine a set of wideband andsubband precoders associated with a configured antenna array;

program code for causing the computer to transmit a precoding matrixindicator (PMI), wherein the PMI is associated with a wideband precodingmatrix selected from a set of predetermined wideband precoders; and

program code for causing the computer to transmit a channel qualityindicator (CQI) generated based on the measured reference signal,wherein the channel quality indicator is generated according to anassumption that precoder elements are cycled from a set of predeterminedsubband precoders.

Based on the seventeenth aspect, the non-transitory computer-readablemedium of an eighteenth aspect,

wherein the CQI includes a single CQI when the rank indicator is >1, and

wherein the CQI includes a first CQI for single port transmissions and asecond CQI when transmit diversity is supported, wherein the second CQIincludes a difference between the first CQI and a diversity CQI for thetransmit diversity.

Based on the seventeenth aspect, the non-transitory computer-readablemedium of a nineteenth aspect, wherein the PMI is not reported when therank indicator is >4, wherein the CQI is generated according to anassumption that precoder elements are cycled from a set of predeterminedwideband precoders.

Based on the seventeenth aspect, the non-transitory computer-readablemedium of a twentieth aspect, further includes:

program code for causing the computer to receive from the base stationconfiguration of a first, second, and third reporting parameters,wherein the rank indicator is transmitted according to a firstperiodicity, the PMI is transmitted according to a second periodicity,and the CQI is transmitted according to a third periodicity, wherein thefirst, second, and third periodicities are based on one or more of thefirst, second, and third reporting parameters.

The present disclosure comprises a twenty-first aspect which furthercomprises the non-transitory computer-readable medium of any combinationthe seventeenth through twentieth aspects.

The present disclosure comprises a twenty-second aspect, such as anapparatus configured for wireless communication, the apparatuscomprising:

at least one processor; and

a memory coupled to the at least one processor,

wherein the at least one processor is configured:

-   -   to select a first precoder associated with a first transmission        block, wherein the first transmission block includes one of: a        first resource block, a first set of bundled resource blocks, or        a first sub-resource block selected as a group of contiguous        resource elements within a resource block;    -   to transmit user equipment (UE)-specific reference signals        (UE-RS) and data within the first transmission block, wherein        the UE-RS and data are precoded using the first precoder;    -   to select a next precoder associated with a next transmission        block, wherein the next transmission block includes one of: a        next resource block, a next set of bundled resource blocks, or a        next sub-resource block selected as a next group of contiguous        resource elements within the resource block; and    -   to transmit the UE-RS and data in the next transmission block,        wherein the UE-RS and data are precoded with a next precoder.

Based on the twenty-second aspect, the non-transitory computer-readablemedium of a twenty-third aspect, wherein the first precoder and the nextprecoder are based on a product of a wideband precoding matrix and asubband precoding matrix, wherein the subband precoding matrix iscyclically selected from a set of predetermined precoding matrices.

Based on the twenty-third aspect, the non-transitory computer-readablemedium of a twenty-fourth aspect, wherein the wideband precoding matrixis one of:

received from a UE; or

randomly selected from a set of predetermined wideband precodingmatrices.

Based on the twenty-second aspect, the non-transitory computer-readablemedium of a twenty-fifth aspect, wherein the configuration of the atleast one processor to transmit the UE-RS and data are performed atrank >1, wherein the data is further precoded with a layer permutationmatrix along with the first precoder and the next precoder; wherein thelayer permutation matrix cyclically assigns each resulting transmissionbeam to a different layer within a predetermined number of continuoussubcarriers.

Based on the twenty-second aspect, the non-transitory computer-readablemedium of a twenty-sixth aspect, wherein the configuration of the atleast one processor to transmit the UE-RS and data are performed at rank1 and configured with transmit diversity, wherein the data is furtherprecoded with a space frequency block coding matrix.

Based on the twenty-sixth aspect, the non-transitory computer-readablemedium of a twenty-seventh aspect, further including configuration ofthe at least one processor:

to determine the first transmission block is the first set of bundledresource blocks;

to determine presence of an even number of resource elements for thedata in two continuous resource blocks of the first set of bundledresource blocks; and

to map the data precoded with the space frequency block coding matrixacross two continuous resource blocks of the first set of bundledresource blocks.

Based on the twenty-second aspect, the non-transitory computer-readablemedium of a twenty-eighth aspect, further including configuration of theat least one processor to transmit an indication of transmission scheme,wherein the indication of transmission scheme is associated with atleast one or more UE-RS ports, the number of useful layers, a mode oftransmit diversity or spatial multiplexing for data transmission.

Based on the twenty-second aspect, the non-transitory computer-readablemedium of a twenty-ninth aspect, further including configuration of theat least one processor to determine the first transmission block and thenext transmission block based on at least a total number of scheduledresource blocks, wherein a sub-resource block is selected only for asmall size resource allocation.

The present disclosure comprises a thirtieth aspect which furthercomprises the non-transitory computer-readable medium of any combinationthe twenty-second through twenty-ninth aspects.

The present disclosure comprises a thirty-first aspect, such as anapparatus configured for wireless communication, the apparatuscomprising:

at least one processor; and

a memory coupled to the at least one processor,

wherein the at least one processor is configured:

-   -   to obtain a first port virtualization matrix for mapping a        predetermined number of antennas into a subset of virtualized        antenna ports;    -   to transmit in a first transmission block a user equipment        (UE)-specific reference signal (UE-RS) precoded with the first        port virtualization matrix, wherein the first transmission block        is one of: a first resource block or a first set of bundled        resource blocks;    -   to precode data using a random beamformer, wherein the random        beamformer includes the first port virtualization matrix and a        second precoding matrix selected from a set of precoding        matrices associated with the subset of virtualized antenna        ports; and    -   to transmit the precoded data in the first transmission block.

Based on the thirty-first aspect, the non-transitory computer-readablemedium of a thirty-second aspect, wherein the configuration of the atleast one processor to obtain the port virtualization matrix includesconfiguration of the at least one processor to one of:

receive the port virtualization matrix from a UE; or

randomly select a set of orthogonal DFT basis vectors from apredetermined wideband codebook for the port virtualization matrix.

Based on the thirty-first aspect, the non-transitory computer-readablemedium of a thirty-third aspect, wherein the configuration of the atleast one processor to transmit the UE-RS and data are performed atrank >1, wherein the data is further precoded with a cyclic delaydiversity matrix and a discrete Fourier transform (DFT) rotationalmatrix along with the random beamformer; wherein the cyclic delaydiversity matrix and the DFT rotation matrix cyclically assign eachresulting transmission beam to a different layer within a predeterminednumber of continuous subcarriers.

Based on the thirty-first aspect, the non-transitory computer-readablemedium of a thirty-fourth aspect, wherein the configuration of the atleast one processor to transmit the UE-RS and data are performed at rank1 and configured with transmit diversity, wherein the data is furtherprecoded with a space frequency block coding matrix.

Based on the thirty-fourth aspect, the non-transitory computer-readablemedium of a thirty-fifth aspect, further including configuration of theat least one processor:

to determine the first transmission block is the first set of bundledresource blocks;

to determine presence of an even number of resource elements for thedata in two continuous resource blocks of the first set of bundledresource blocks; and

to map the data precoded with the space frequency block coding matrixacross two resource blocks of the first set of bundled resource blocks.

Based on the thirty-first aspect, the non-transitory computer-readablemedium of a thirty-sixth aspect, further including configuration of theat least one processor to transmit an indication of transmission scheme,wherein the indication of transmission scheme is associated with atleast one or more UE-RS ports, the number of useful layers, a mode oftransmit diversity or spatial multiplexing for data transmission.

The present disclosure comprises a thirty-seventh aspect which furthercomprises the non-transitory computer-readable medium of any combinationthe thirty-first through thirty-sixth aspects.

The present disclosure comprises a thirty-eighth aspect, such as anapparatus configured for wireless communication, the apparatuscomprising:

at least one processor; and

a memory coupled to the at least one processor,

wherein the at least one processor is configured:

-   -   to measure a reference signal received from a base station;    -   to determine a set of wideband and subband precoders associated        with a configured antenna array;    -   to transmit a precoding matrix indicator (PMI), wherein the PMI        is associated with a wideband precoding matrix selected from a        set of predetermined wideband precoders; and    -   to transmit a channel quality indicator (CQI) generated based on        the measured reference signal, wherein the channel quality        indicator is generated according to an assumption that precoder        elements are cycled from a set of predetermined subband        precoders.

Based on the thirty-eighth aspect, the non-transitory computer-readablemedium of a thirty-ninth aspect,

wherein the CQI includes a single CQI when the rank indicator is >1, and

wherein the CQI includes a first CQI for single port transmissions and asecond CQI when transmit diversity is supported, wherein the second CQIincludes a difference between the first CQI and a diversity CQI for thetransmit diversity.

Based on the thirty-eighth aspect, the non-transitory computer-readablemedium of a fortieth aspect, wherein the PMI is not reported when therank indicator is >4, wherein the CQI is generated according to anassumption that precoder elements are cycled from a set of predeterminedwideband precoders.

Based on the thirty-eighth aspect, the non-transitory computer-readablemedium of a forty-first aspect, further including configuration of theat least one processor to receive from the base station configuration ofa first, second, and third reporting parameters, wherein the rankindicator is transmitted according to a first periodicity, the PMI istransmitted according to a second periodicity, and the CQI istransmitted according to a third periodicity, wherein the first, second,and third periodicities are based on one or more of the first, second,and third reporting parameters.

The present disclosure comprises a forty-second aspect which furthercomprises the non-transitory computer-readable medium of any combinationthe thirty-eighth through forty-first aspects.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

The functional blocks and modules described herein may compriseprocessors, electronics devices, hardware devices, electronicscomponents, logical circuits, memories, software codes, firmware codes,etc., or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure. Skilled artisans will also readilyrecognize that the order or combination of components, methods, orinteractions that are described herein are merely examples and that thecomponents, methods, or interactions of the various aspects of thepresent disclosure may be combined or performed in ways other than thoseillustrated and described herein.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented thorugh computer-executable instructions in hardware,software, firmware, or any combination thereof. If implemented insoftware, the functions may be stored on or transmitted over as one ormore instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. Computer-readable storagemedia may be any available media that can be accessed by a generalpurpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, a connection may be properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, or digital subscriber line (DSL), then the coaxial cable,fiber optic cable, twisted pair, or DSL, are included in the definitionof medium. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andblu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

As used herein, including in the claims, the term “and/or,” when used ina list of two or more items, means that any one of the listed items canbe employed by itself, or any combination of two or more of the listeditems can be employed. For example, if a composition is described ascontaining components A, B, and/or C, the composition can contain Aalone; B alone; C alone; A and B in combination; A and C in combination;B and C in combination; or A, B, and C in combination. Also, as usedherein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of indicates a disjunctive list such that, forexample, a list of “at least one of A, B, or C” means A or B or C or ABor AC or BC or ABC (i.e., A and B and C) or any of these in anycombination thereof.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method of wireless communication, comprising:selecting a first precoder associated with a first transmission block,wherein the first transmission block includes one of: a first resourceblock, a first set of bundled resource blocks, or a first sub-resourceblock selected as a group of contiguous resource elements within aresource block; transmitting user equipment (UE)-specific referencesignals (UE-RS) and data within the first transmission block, whereinthe UE-RS and data are precoded using the first precoder; selecting anext precoder associated with a next transmission block, wherein thenext transmission block includes one of: a next resource block, a nextset of bundled resource blocks, or a next sub-resource block selected asa next group of contiguous resource elements within the resource block;and transmitting the UE-RS and data in the next transmission block,wherein the UE-RS and data are precoded with a next precoder.
 2. Themethod of claim 1, wherein the first precoder and the next precoder arebased on a product of a wideband precoding matrix and a subbandprecoding matrix, wherein the subband precoding matrix is cyclicallyselected from a set of predetermined precoding matrices.
 3. The methodof claim 2, wherein the wideband precoding matrix is one of: receivedfrom a UE; or randomly selected from a set of predetermined widebandprecoding matrices.
 4. The method of claim 1, wherein the transmittingthe UE-RS and data are at rank >1 and configured with spatialmultiplexing, wherein the data is further precoded with a layerpermutation matrix along with the first precoder and the next precoder;wherein the layer permutation matrix cyclically assigns each resultingtransmission beam to a different layer within a predetermined number ofcontinuous subcarriers.
 5. The method of claim 1, wherein thetransmitting the UE-RS and data are at rank 1 and configured withtransmit diversity, wherein the data is further precoded with a spacefrequency block coding matrix.
 6. The method of claim 5, furtherincluding: determining the first transmission block is the first set ofbundled resource blocks; determining presence of an even number ofresource elements for the data in two continuous resource blocks of thefirst set of bundled resource blocks; and mapping the data precoded withthe space frequency block coding matrix across two continuous resourceblocks of the first set of bundled resource blocks.
 7. The method ofclaim 1, further including: transmitting an indication of transmissionscheme, wherein the indication of transmission scheme is associated withat least one or more UE-RS ports, the number of useful layers, a mode oftransmit diversity or spatial multiplexing for data transmission.
 8. Themethod of claim 1, further including: determining the first transmissionblock and the next transmission block based on at least a total numberof scheduled resource blocks, wherein a sub-resource block is selectedonly for a small size resource allocation.
 9. (canceled)
 10. A method ofwireless communication, comprising: measuring a reference signalreceived from a base station; determining a set of wideband and subbandprecoders associated with a configured antenna array; transmitting aprecoding matrix indicator (PMI), wherein the PMI is associated with awideband precoding matrix selected from a set of predetermined widebandprecoders; and transmitting a channel quality indicator (CQI) generatedbased on the measured reference signal, wherein the channel qualityindicator is generated according to an assumption that precoder elementsare cycled from a set of predetermined subband precoders.
 11. The methodof claim 10, wherein the CQI includes a single CQI when a rank indicatoris >1.
 12. The method of claim 10, wherein the PMI is not reported whenthe a rank indicator is >4, wherein the CQI is generated according to anassumption that precoder elements are cycled from a set of predeterminedwideband precoders.
 13. The method of claim 10, further includingtransmitting a rank indicator, wherein the rank indicator corresponds toone of: a mode of transmit diversity or spatial multiplexing for datatransmission; or a number of useful layers in a transmission channel.14. The method of claim 10, further including: receiving from the basestation configuration of a first, second, and third reportingparameters, wherein the rank indicator is transmitted according to afirst periodicity, the PMI is transmitted according to a secondperiodicity, and the CQI is transmitted according to a thirdperiodicity, wherein the first, second, and third periodicities arebased on one or more of the first, second, and third reportingparameters.
 15. (canceled)
 16. An apparatus configured for wirelesscommunication, comprising: means for randomly selecting a first precoderassociated with a first transmission block, wherein the firsttransmission block includes one of: a first resource block, a first setof bundled resource blocks, or a first sub-resource block selected as agroup of contiguous resource elements within a resource block; means fortransmitting user equipment (UE)-specific reference signals (UE-RS) anddata within the first transmission block, wherein the UE-RS and data areprecoded using the first precoder; means for selecting a next precoderassociated with a next transmission block, wherein the next transmissionblock includes one of: a next resource block, a next set of bundledresource blocks, or a next sub-resource block selected as a next groupof contiguous resource elements within the resource block; and means fortransmitting the UE-RS and data in the next transmission block, whereinthe UE-RS and data are precoded with a next precoder.
 17. The apparatusof claim 16, wherein the first precoder and the next precoder are basedon a product of a wideband precoding matrix and a subband precodingmatrix, wherein the subband precoding matrix is cyclically selected froma set of predetermined precoding matrices.
 18. The apparatus of claim17, wherein the wideband precoding matrix is one of: received from a UE;or randomly selected from a set of predetermined wideband precodingmatrices.
 19. The apparatus of claim 16, wherein the means fortransmitting the UE-RS and data are performed at rank >1, wherein thedata is further precoded with a layer permutation matrix along with thefirst precoder and the next precoder; wherein the layer permutationmatrix cyclically assigns each resulting transmission beam to adifferent layer within a predetermined number of continuous subcarriers.20. The apparatus of claim 16, wherein the means for transmitting theUE-RS and data are performed at rank 1 and configured with transmitdiversity, wherein the data is further precoded with a space frequencyblock coding matrix.
 21. The apparatus of claim 20, further including:means for determining the first transmission block is the first set ofbundled resource blocks; means for determining presence of an evennumber of resource elements for the data in two continuous resourceblocks of the first set of bundled resource blocks; and means formapping the data precoded with the space frequency block coding matrixacross two continuous resource blocks of the first set of bundledresource blocks.
 22. The apparatus of claim 16, further including: meansfor transmitting an indication of transmission scheme, wherein theindication of transmission scheme is associated with at least one ormore UE-RS ports, the number of useful layers, a mode of transmitdiversity or spatial multiplexing for data transmission.
 23. Theapparatus of claim 16, further including: means for determining thefirst transmission block and the next transmission block based on atleast a total number of scheduled resource blocks, wherein asub-resource block is selected only for a small size resourceallocation.
 24. (canceled)
 25. An apparatus configured for wirelesscommunication, comprising: means for measuring a reference signalreceived from a base station; means for determining a set of widebandand subband precoders associated with a configured antenna array; meansfor transmitting a rank indicator, wherein the rank indicatorcorresponds to a number of useful layers in a transmission channel;means for transmitting a precoding matrix indicator (PMI), wherein thePMI is associated with a wideband precoding matrix selected from a setof predetermined wideband precoders; and means for transmitting achannel quality indicator (CQI) generated based on the measuredreference signal, wherein the channel quality indicator is generatedaccording to an assumption that precoder elements are cycled from a setof predetermined subband precoders.
 26. The apparatus of claim 25,wherein the CQI includes a single CQI when the rank indicator is >1, andwherein the CQI includes a first CQI for single port transmissions and asecond CQI when transmit diversity is supported, wherein the second CQIincludes a difference between the first CQI and a diversity CQI for thetransmit diversity.
 27. The apparatus of claim 25, wherein the PMI isnot reported when the rank indicator is >4, wherein the CQI is generatedaccording to an assumption that precoder elements are cycled from a setof predetermined wideband precoders.
 28. The apparatus of claim 25,further including: means for receiving from the base stationconfiguration of a first, second, and third reporting parameters,wherein the rank indicator is transmitted according to a firstperiodicity, the PMI is transmitted according to a second periodicity,and the CQI is transmitted according to a third periodicity, wherein thefirst, second, and third periodicities are based on one or more of thefirst, second, and third reporting parameters.
 29. (canceled)